phrases derive from the same set of software user rights formulated in the late 1980s by Richard Stallman of the Free Software Foundation. The goals of the MITRE study were to develop as complete a listing of FOSS applications used in the DoD as possible, and to collect representative examples of how those applications are being used. Over a two-week period the survey identified a total of 115 FOSS applications and 251 examples of their use. To help analyze the resulting data, the hypothetical question was posed of what would happen if FOSS software were banned in the DoD. Surprisingly, over the course of the analysis it was discovered that this hypothetical question has a real-world analog in the form of proprietary licenses that if widely used would effectively ban most forms of FOSS. For the purpose of the analysis, the effects of the hypothetical ban were evaluated based on how FOSS is currently being used in survey examples. In the case of niche-dominating FOSS products such as Sendmail (ubiquitous for Internet email) and GCC (a similarly ubiquitous compiler), a large amplification factor must also be taken into account when estimating such impacts. The actual levels of DoD use of such ubiquitous applications is likely to be hundreds, thousands, or even tens of thousands of time larger than the number of examples identified in the brief survey. The main conclusion of the analysis was that FOSS software plays a more critical role in the DoD than has generally been recognized. FOSS applications are most important in four broad areas: Infrastructure Support, Software Development, Security, and Research. One unexpected result was the degree to which Security depends on FOSS. Banning FOSS would remove certain types of infrastructure components (e.g., OpenBSD) that currently help support network security. It would also limit DoD access to—and overall expertise in—the use of powerful FOSS analysis and detection applications that hostile groups could use to help stage cyberattacks. Finally, it would remove the demonstrated ability of FOSS applications to be updated rapidly in response to new types of cyberattack. Taken together, these factors imply that banning FOSS would have immediate, broad, and strongly negative impacts on the ability of many sensitive and security-focused DoD groups to defend against cyberattacks. For Infrastructure Support, the strong historical link between FOSS and the advent of the Internet means that removing FOSS applications would result in a strongly negative impact